Trifluoromethyl group palladium catalysts

Catalysts (25) are the Lewis acid-Lewis base bifunctional catalysts in which Lewis acid-Al(III) moiety activates acyl iminium ion and the Lewis base (oxygen of phosphine oxide) does TMSCN, simultaneously (Scheme 5.7). Halogen atoms at the 6-position enhanced both yields and enantioselectivity in Reissert-type cyanation of the imino part of 26. However, the order for the activation is not parallel to the electronegativity of the halogen atoms and, moreover, the strong electron-withdrawing trifluoromethyl group provided unexpectedly the worst result for the activation [13]. It is not simple to explain this phenomenon only in terms of the increased Lewis acidity of the metal center. Trifluoromethylated BINOL-zirconium catalysts (28) for asymmetric hetero Diels-Alder reaction (Scheme 5.8) [14], trifluoromethylated arylphosphine-palladium catalyst (32) for asymmetric hydrosilylation (Scheme 5.9) [15], and fluorinated BINOL-zinc catalyst (35) for asymmetric phenylation (Scheme 5.10) [16] are known. 

To make the transformation even more useful, different carbon electrophiles should be connected sequentially in a stepwise manner. For this purpose, a transition-metal-catalyzed cross-coupling reaction opened the way. As shown in Scheme 22, cinnamyl chloride is treated with bis(iodozincio)methane (3) in the presence of palladium catalyst with various phosphine ligands. Phosphine ligands, having an electron-withdrawing group, such as tris[3,5-bis(trifluoromethyl)phenyl]phosphine and tris(2-furanyl)phosphine, show excellent results47. 

Aqueous aminations with palladium catalysts that are not soluble in water have recently been described by Buchwald et al. [4]. The use of 2/Pd2dba3 and KOH in water without co-solvent gives excellent results in the amination of aryl chlorides containing nitro, trifluoromethyl, or pyridyl groups. Indoles and hindered aryl nonaflates can be aminated in good yields. In summary, co-solvents and phase-transfer catalysts are not necessary. 

Chlorine substituents may be replaced by hydrogen by reductive dehalogenation with, for example, Raney nickel or palladium-charcoal catalyst. The 1,7-phenanthroline skeleton is not reduced under these conditions.96,171,172 The bromine group in 4-bromo-2-trifluoromethyl-... 

Brookhart s catalysts Mixture of [N,N -(1,2-dimethyl-1,2-ethanediylidene)bis[2,6-bis(1-methylethyl)benzenamine-KappaA/]] methyl[1,1 -oxybis[ethane]]palladium(1 +) tetrakis[3,5-bis(trifluoromethyl)phenyl] borate(1") and the same complex but with "(acetonitrile)" group instead of "[1,1 -oxybis[ethane]j" group. 

The reaction mechanism is postulated to go through a Heck-like four-membered ring transition state as determined through experimental and theoretical analysis. The addition of water to the reaction did not lower the yield, and the use of palladium acetate in place of the copper catalyst gave no product Importantly, the presence of the alkene group provides a useful handle for further functionalized trifluoromethyl-ated compounds. 

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